German mechanical engineering firm Herrenknecht is building one of the longest tunnel boring machines in the world for the construction of the new 57 km Gotthard railway tunnel in Switzerland. When completed it will be the world’s longest railway tunnel. The tunnel goes up to 2300 metres deep in the mountain and the hardness of the rock places extremely high demands on all machine components. It is for this reason that Herrenknecht decided to use Parker Hannifin’s Ermeto EO2 fittings.
No day trip through the rocks
“This will most certainly be no day trip,” says Jörg Meyer, manager of hydraulics at Herrenknecht. With a length of 410 metres, this machine is one of the longest tunnel borers in the world. It has a diameter of 8,8 metres, is as high as a house and weighs 3050 tons.
Vibrations the greatest challenge
Parker Hannifin will supply the latest connector technology from its Ermeto division. EO2-Form fittings are seated in the front section of the boring machine, where the demand on all components is at its greatest. It is here that extreme vibrations during the boring of the rock occur; there is a danger of rockfalls, and high temperatures and moisture must also be reckoned with.
Frank Simmang, purchasing and materials manager at Herrenknecht, knows only too well the enormous loads involved and recognises the extreme demands on the fittings. “Vibrations are one of the greatest challenges for the components. With hard rock machines problems can occur at the front in the boring head area where the tools are working in bare rock. We cannot get very far with the usual bite-type rings; but we can now eliminate these problems with the EO2-Form system,” he says.
EO2 sealing ring and cold forming
Herrenknecht fits EO2-Form fittings not only in the hydraulic circuits but also on the tubing with which railings are built onto the machine. The high load bearing capacity of this system was one of the most important selection criteria for the hydraulics manager. “We simply need safe connectors in our machines,” says Meyer. On this basis he is convinced of the advantages of EO2-Form fittings.
Features of this fitting are the classical EO2 sealing ring and the cold forming of the tube. Here the large volume elastomeric seal plays a prominent part, especially when used in hydraulic circuits. The elastomer effectively blocks the one possible leak path between the internal cone of the fitting body and the tube surface. The seal geometry is designed so that the sealing effect is supported by the system pressure.
A logically shaped and safe fitting
The logically shaped and safe fitting convinced the hydraulics manager during the first tests carried out by Herrenknecht. “Bite type fittings would be tightened up until they would go no further and technicians would then have problems during tunnel boring. We can now avoid these difficulties with the EO2-Form system,” Meyer says.
Cold-forming tubes make a big contribution to this. To assemble, the EO2 sealing ring is simply pushed onto the tube and the nut tightened, enabling connections to be made simply and quickly. The power transmission load is taken on not by the tube surface but rather by the reinforced sealing ring. High mechanical strength and maximum pull-out strength are the result.
We place the greatest value on safety
“We place great value on safety requirements,” says Meyer. ”Whilst we must avoid leakage in the hydraulic connections, the tubes assembled as rails, for example on the platforms of the machines, must not tear off because of extreme vibrations or rockfalls.”
“It is great for us to hear from customers how our products fullfil their requirements and perform under these hard conditions and I am sure that there are similar conditions in the mining sector in South Africa where Parker Hannifin’s fittings can be applied,” says Oliver Helterhof, group business development manager – Africa at Parker Hannifin.
For more information contact Mark Johnson, Parker Hannifin, +27 (0)11 961 0700, [email protected], www.parker.com/za
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| www: | www.parker.com/za |
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